Due to advantages of good formability, high dimensional precision, high magnetic properties or the like, rare-earth bonded permanent magnets have been widely used in fields including various electronic equipment, office automation, automobiles etc., especially in micro-special motors. In order to meet the requirements of equipment miniaturization and microminiaturization in scientific and technological development, it is necessary to further optimize the properties of bonded magnetic powder.
The key to prepare a bonded rare-earth permanent magnet is a preparation of rare-earth permanent magnetic powder. The properties of the magnetic powder determine the quality and market price of the bonded magnet directly. Mature bonded rare-earth permanent magnets in the early market are basically isotropic bonded NdFeB magnets. This kind of widely used NdFeB magnetic powder is generally prepared by a rapid quenching method. Such NdFeB magnets have good properties. However, as patent products, the NdFeB magnets have been controlled by a few companies. In order to extend the application of rare-earth bonded permanent magnetic products further, people have been struggling to find more new bonded permanent magnetic powder products in recent years. Bonded permanent magnetic powder including HDDR (hydrogenation-disproportionation-desorption-recombination) isotropic powder, Th2Zn17-type isotropic powder, TbCu7-type isotropic powder and ThMn12-type isotropic powder etc. has attracted much attention of people.
Currently, samarium-iron-nitrogen-series rare-earth permanent magnetic powder has attracted wide attention because of its excellent properties. During a preparation process of the SmFe-series alloy, a rapidly quenched magnetic powder with a TbCu7-structure hard magnetic phase is prepared through a strip casting technique. However, the preparation process, especially an industrial process has the following problems:
(1) samarium, with a low vapor pressure, is seriously volatile during the preparation process, thus causing unstable alloy preparation costs; the volatilized samarium, which is easily oxidized, is easy to catching fire and cause safety accidents; the volatilized samarium blocks a pipeline, which greatly damages a vacuum system;
(2) the highly viscous samarium alloy with bad wettability with a copper wheel during the rapid quenching process is easy to cause alloy liquid splashing, unstable liquid flows on the surface of a strip casting and unevenness of the surface to further cause an uneven alloy phase structure and microstructure, reducing the magnetic properties of the prepared samarium-iron-nitrogen-series rare-earth permanent magnetic powder. This is also a major reason that influences large scale application of the material currently.
In order to solve these problems encountered during the preparation process of the samarium iron alloy, it is a new subject in the field of rare-earth permanent magnetic powder development to find a kind of new rare-earth permanent magnetic powder with better magnetic properties.